Jim Flanagan wrote:
after warmup, I need to tweak the temp for a freq MIN. Whereas, for an SC
cut xtal osc we would be looking for a freq MAX. For both xtal cuts the
turning
point is typically set for somewhere in the 75 - 85 C range. I see
Jim
jf...@tampabay.rr.com
The majority of 10811 SC-cut crystals do not have a temperature
turnover. Instead they have an inflection point where the tempco is
minimum, but not zero. It is fairly broad, so the oven set point is
not especially critical. If you want to tweak something in the 10811,
better to tweak the resistors that apportion heater power to the
two transistors, to maximum thermal gain.
In the case of an oscillator that does have a turnover, you do not
necessarily want to set the oven temperature to the turnover. Instead
you want to offset it so that there is a nonzero crystal tempco that
happens to cancel out the tempco of the oscillator electronics.
Rick Karlquist N6RK
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